# Covergance Problem in Transient Bias Point Calculation

#### a.bunga

##### Newbie level 2
hi, i am new here. i can't stimulate my circuit? why my circuit has been paused becaused of this error? i need your help to help me with this error (PSPICE). thank you

this the error :

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**** 05/23/20 11:38:39 ********* PSpice 9.2 (Mar 2000) ******** ID# 1 ********

** Profile: "SCHEMATIC1-analog ct_ha"  [ d:\145730\proposal\analog\analog circuit ha-schematic1-analog ct_ha.sim ]

****     Voltage Controlled Switch MODEL PARAMETERS

******************************************************************************

X_U4.Smod
RON     .01
ROFF    1.000000E+06
VON    1
VOFF    0

ERROR -- Convergence problem in transient bias point calculation

Last node voltages tried were:

NODE   VOLTAGE     NODE   VOLTAGE     NODE   VOLTAGE     NODE   VOLTAGE

(N00617)    -.0794 (N00634)    -.8735 (N00705)    -.8901 (N00779)    -.1842

(N00806)    -.1842 (N00863)    -.4245 (N01105)    -.1842 (N01131)    -.1840

(N01268)    -.1875 (N01485)    -.4301 (N01730)    -.1875 (N01763)    0.0000

(N01859)    0.0000 (N01933)    6.5691 (N02282)    -.1875 (X_U4.3)    0.0000

(X_IC1.3)    -.1842                   (X_IC1.4)     .6043

(X_IC1.5)     .1814                   (X_IC1.6) 153.5E-06

(X_IC1.7)     .4607                   (X_IC1.8)     .6042

(X_IC1.9)    -.0980                   (X_IC2.3)    -.1875

(X_IC2.4)     .5988                   (X_IC2.5)     .1814

(X_IC2.6) 132.2E-06                   (X_IC2.7)     .4551

(X_IC2.8)     .5987                   (X_IC2.9)    -.0996

(X_IC1.10) 726.4E-18                  (X_IC1.11)   -1.4598

(X_IC1.12)    1.4598                  (X_IC1.13)-1.914E-15

(X_IC1.14)   -1.4598                  (X_IC1.15)    1.4598

(X_IC1.16)-1.914E-15                  (X_IC1.17)   -1.4598

(X_IC1.18)    -.3188                  (X_IC1.19)   -1.6230

(X_IC1.20)     .9854                  (X_IC1.21)    -.2327

(X_IC1.22)    -.2327                  (X_IC1.23)    -.1698

(X_IC1.24)    -.1240                  (X_IC1.25)    -.2661

(X_IC1.26)    -.3188                  (X_IC1.27)    -.0905

(X_IC1.28)    -.4368                  (X_IC1.29)    -.1840

(X_IC1.30)    1.0860                  (X_IC1.31)   -1.4540

(X_IC1.32)    -.7048                  (X_IC1.33)   50.4070

(X_IC1.35)    1.4598                  (X_IC1.36)    -.2828

(X_IC1.51)    0.0000                  (X_IC1.97)    -.6376

(X_IC1.98)    -.3188                  (X_IC2.10) 726.4E-18

(X_IC2.11)   -1.4598                  (X_IC2.12)    1.4598

(X_IC2.13)-1.914E-15                  (X_IC2.14)   -1.4598

(X_IC2.15)    1.4598                  (X_IC2.16)-1.914E-15

(X_IC2.17)   -1.4598                  (X_IC2.18)    -.3248

(X_IC2.19)   -1.6350                  (X_IC2.20)     .9854

(X_IC2.21)    -.2371                  (X_IC2.22)    -.2371

(X_IC2.23)    -.1731                  (X_IC2.24)    -.1263

(X_IC2.25)    -.2663                  (X_IC2.26)    -.3248

(X_IC2.27)    -.0922                  (X_IC2.28)    -.4450

(X_IC2.29)    -.1875                  (X_IC2.30)    1.0825

(X_IC2.31)   -1.4575                  (X_IC2.32)    -.7053

(X_IC2.33)   50.4080                  (X_IC2.35)    1.4598

(X_IC2.36)    -.2867                  (X_IC2.51)    0.0000

(X_IC2.97)    -.6497                  (X_IC2.98)    -.3248

(X_Speaker.c)    0.0000               (X_Speaker.res)     .0438

(X_Speaker.temp)  218.9700            (X_Speaker.ambnt)  218.9700

These supply currents failed to converge:

I(X_IC2.EP)               =    10.00GA  \    10.00GA
I(X_IC2.EM)               =   -10.00GA  \   -10.00GA
I(X_IC2.V2)               =   -10.00GA  \   -10.00GA
I(X_IC2.V3)               =   -10.00GA  \   -10.00GA

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##### Super Moderator
Staff member
10.00 GA indicates giga-Amps, correct? That's a very large value. Try putting resistors in series with capacitors. Your schematic has the power supply feeding a capacitor directly. The simulator cannot calculate a sensible RC time constant.

#### BigBoss

##### Advanced Member level 5
Remove U4 Switch.You don't need it.
That switch disturbs the simulation..not necessary..

a.bunga and FvM

points: 2

### a.bunga

points: 2

#### a.bunga

##### Newbie level 2
why the switch need to be remove? i got the graph when i remove the switch as you told.

#### KlausST

##### Super Moderator
Staff member
Hi,

The answer is already given in post#2.
A closing "ideal" switch with two "ideal" capacitors gives "infinite" current at zero charging time.

--> Neither "infinite current" nor "zero time" can be simulated correctly.

*********
So far so good.
As soon as one does a realistic simulation, with wire resistance, with wire impedance, with ESR at the capacitors, with contact resistance....the above simulation will work, too.

Now think the other way round: How much sense makes an "unrealistic ideal" simulation at all?
It does not show how the circuit really works.

If you want to do a really realistic simulation you need to include additional parameters of each part and you need to add the PCB layout effects.

But I don't want to say that simulation is useless. But you (the designer) needs to know the limits. What does the simulation show ... and what does the simulation not show. You need to interprete the simulation results

Klaus